Solubilization and Characterization of Phosphoprotein Phosphatase(s) from Bovine Corpus-Luteum Plasma Membranes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65607/1/j.1432-1033.1975.tb02186.x.pd

Distribution of parathyroid hormone-stimulated adenylate cyclase in plasma membranes of cells of the kidney cortex

Free flow electrophoresis was employed to separate renal cortical plasma membranes into luminal (brush border microvilli) and contraluminal (basal-lateral membrane) fractions. During the separation adenylate cyclase activity was found to parallel the activity of Na+-K+-activated ATPase, an enzyme which is present in contraluminal but not in luminal membranes. In the basal-lateral membrane fraction the specific activities of adenylate cyclase and Na+-K+-activated ATPase were 4.4 and 4.6 times greater, respectively, than in the brush border fraction. The adenylate cyclase of the basal-lateral membrane fraction was specifically stimulated by parathyroid hormone which maximally increased enzyme activity eightfold. The biologically active (1-34) peptide fragment of paratyhroid hormone produced a 350% increase in adenylate cyclase activity. In contrast, calcitonin, epinephrine and vasopressin maximally stimulated the enzyme by only 55, 35 and 30%, respectively. These results indicate that adenylate cyclase, specifically stimulated by parathyroid hormone, is distributed preferentially in the contraluminal region of the plasma membrane of renal cortical epithelial cells

Distribution of membrane-bound cyclic AMP-dependent protein kinase in plasma membranes of cells of the kidney cortex

Renal cortical plasms membranes were separated by free flow electrophoresis into luminal (brush border microvilli) and contraluminal (basal-lateral membrane) fractions. These membranes were found to contain an intrinsic, self-phosphorylating system which consists of a cyclic AMP-dependent protein kinase, a phosphorprotein phosphatase and the substrate(s) of these enzymes. The kinase, but not the phosphatase, was stimulated by cyclic AMP; maximal (1.7-fold) stimulation was effected at a cyclic AMP concentration of 0.1 muM. The degree of phosphorylation of the brush borders was six times greater than that of the basal-lateral membranes in the absence of cyclic AMP and 2.3-fold greater in the presence of cyclic AMP. This preferential phosphorylation of the luminal membrane by membrane-associated protein kinase(s) may play a role in the parathyroid hormone-mediated alterations of solute reabsorption in the proximal tubule

Target Cell Polarity and Membrane Phosphorylation in Relation to the Mechanism of Action of Antidiuretic Hormone

The plasma membrane of the bovine renal collecting duct epithelial cell has been resolved into its apical (luminal) and basal-lateral (contraluminal) components by free flow electrophoresis. The contraluminal, but not the luminal, membrane was found to contain antidiuretic hormone-sensitive adenylate cyclase. The luminal membrane was found to contain a cyclic 3′:5′-adenosine monophosphate-sensitive self-phosphorylating system consisting of a membrane-bound protein kinase and its membrane-bound substrate(s); this intrinsic protein kinase was not present in the contraluminal membrane. These findings provide direct evidence that the initiating steps in the action of antidiuretic hormone on the kidney take place at the contraluminal pole of the hormonesensitive target cell and that the late or terminal steps occur at the luminal pole, where they involve an alteration in the level of membrane phosphorylation

Compartmentalized autocrine signaling to cystic fibrosis transmembrane conductance regulator at the apical membrane of airway epithelial cells

Physical stimulation of airway surfaces evokes liquid secretion, but the events that mediate this vital protective function are not understood. When cystic fibrosis transmembrane conductance regulator (CFTR) channel activity was used as a functional readout, we found signaling elements compartmentalized at both extracellular and intracellular surfaces of the apical cell membrane that activate apical Cl(−) conductance in Calu-3 cells. At the outer surface, ATP was released by physical stimuli, locally converted to adenosine, and sensed by A(2B) adenosine receptors. These receptors couple to G proteins, adenylyl cyclase, and protein kinase A, at the intracellular face of the apical membrane to activate colocalized CFTR. Thus, airways have evolved highly efficient mechanisms to “flush” noxious stimuli from airway surfaces by selective activation of apical membrane signal transduction and effector systems